The instant invention is related to a composition and method of making microemulsion blends having an average particle size of from about 0.001 microns to about 0.05 microns whereby the blend comprises at least one volatile silicone and a silicone capable of forming microemulsions. The instant invention is further related to personal care products comprising said microemulsion blends comprising one or more volatile silicones.
Microemulsions containing silicone fluids have been found to be useful in a variety of personal care products such as hair conditioners and other cosmetic formulations. As defined herein, the term "microemulsions" refers to transparent, mechanically and thermally stable systems comprising small droplets having a mean or average particle diameter usually not more than 0.05 microns in diameter, preferably not more than 0.040 microns in diameter and most preferably not more than 0.025 microns in diameter. The small size of the droplets imparts a high degree of transparency to the emulsion. Cosmetic formulations containing microemulsions possess improved aesthetic values as well as improved physical properties.
The use of microemulsions in cosmetic applications is known in the art, see for example U.S. Pat. Nos. 4,797,272 (Linn et al.) and 4,620,878 (Gee). U.S. Pat. No. 4,797,272 to Linn et al. discloses water-in-oil microemulsion compositions having a mean droplet size ranging from about 0.001 microns to about 0.200 microns and containing moisturizers or sunscreens, surfactants, oils (e.g. cyclic dimethyl polysiloxanes), and skin humectants. U.S. Pat. No. 4,620,878 to Gee discloses a polyorganosiloxane emulsion that contains a polyorganosiloxane containing at least one polar radical such as an amino radical attached to the silicon of the siloxane by Si--C or Si--O--C bonds or at least one silanol radical and a surfactant that is insoluble in the polyorganosiloxane. The emulsion prepared by Gee has an average particle size of less than 0.14 microns and can be prepared by forming a translucent oil concentrate by mixing the polyorganosiloxane, at least one surfactant, and water and then forming a polyorganosiloxane emulsion of the oil-in-water type by rapidly dispersing the translucent oil concentrate in water.
Microemulsions of volatile silicones are taught in the art, for example U.S. Pat. Nos. 4,782,095 and 4,801,447, however these microemulsions have required large amounts of surfactants. The high levels of surfactants required in the prior art applications are detrimental in many applications. For example, in hair conditioners, such high surfactant levels lead to excessive foaming and poor tactile properties.
While microemulsions of aminofunctional silicones provide beneficial conditioning results when applied to damaged hair tresses they provide little benefit in wet combing. In contrast, volatile silicones provide excellent wet combing properties. It continues to be desirable to provide alternative or improved methods for preparing microemulsion blends of small average particle size that comprise volatile silicones.